On the Energy Highway with David A. “All watts are not created equal.”
I was quite taken with comments by David A. on my water wheel post, and am posting the discussion here in case others are interested.
Note: This is not a climateball playing field, so ideas and facts are welcome, but not disparaging remarks. Comments containing the latter will be deleted.
On April 24, David A. Said:
Good Article IMV.
“The energy represented by a solar photon spends an average 43 hours in the Earth system before it is lost to space. Some spend just a millisecond while a very, very tiny percentage might get absorbed in the deep ocean and spend a thousand years on Earth or longer.”
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A Law if you will; “Only two things can affect the energy content of a system in a radiative balance, either a change in the input, or a change in the residence time of some aspect of the energy within the system.”
In ALL cases not involving disparate solar insolation changes, the residence time of the energy must be understood in order to quantify the warming or cooling degree. For instance, clouds are capable of both increasing the residence time of some LWIR radiation from the surface, and decreasing the residence time of SW insolation from the Sun. The net affect is dependent on both the amount of energy affected, and the residence time of the energy affected, which is dependent on both the WL of the energy, and the materials said energy encounters.
I would like to clarify my residence time with a traffic analogy. Numbers are simplified to a ten basis, for ease of math and communication. Picture the earths system (Land, ocean and atmosphere) as a one lane highway. Ten cars per hour enter, (TSI) and ten cars per hour exit (representing radiation to space.) The cars (representing one watt per square meter) are on the highway for one hour. So there are ten cars on the highway. (the earth’s energy budget)
Now let us say the ten cars instantly slow to a ten hour travel time. Over a ten hour period, the energy budget will increase from ten cars, to 100 cars, with no change of input. Let us say we move to a one hundred hour travel time. Then there will be, over a one hundred hour time period, an increase of 990 cars.
Of course the real earth has thousands of lanes traveling at different speeds, and via conduction, convection, radiation, evaporation, condensing, albedo changes, GHGs, etc, etc, trillions of cars constantly changing lanes, with some on the highway for fractions of a second, and some for centuries. Also The sun changes WL over its polarity cycles far more then it changes total TSI. Additionally the sun can apparently enter phases of more active, or less active cycles which last for many decades.
Some factors increase residence time in the atmosphere (GHG) but may reduce energy entering a long term residence like the oceans. For Instance, W/V clear sky conditions, greatly reduces surface insolation at disparate W/L. Such thoughts caused me to question the disparate contributions to earth’s total energy budget of SWR verses LWIR.
Such thought are cause for me to question the total amount of geothermal heat within the oceans, as many of these cars are on a very slow, century’s long lane.
It is true that 100 watts per sq. M of SWR, has the same energy as 100 watts per sq. M of LWIR, however their affect on earth’s energy balance can be dramatically different. In this sense, not all watts are equal.
For instance lets us say 100 watts of LWIR back radiation strikes the ocean surface. That energy then accelerates evaporation where said energy is lifted to altitude, and then condenses, liberating some of that energy to radiate to space. Now lets us assume the same 100 watts per sq M strikes the ocean, but this time it is composed of SWR, penetrating up to 800 ‘ deep. Some of that energy may stay with in the ocean for 800 years. The SWR has far more long term energy, and even warming potential then the LWIR.
Now, let us say the sun enters a multi-decadal increased active phase, and the SWR W/L which deeply penetrates the ocean surface is .1 Watt per sq meter higher then previously. his .01 watt increase, due to the very long residence time, now accumulates in the ocean for the entire multi decadal solar increase.
The oceans are a three dimensional SW selective surface, and should never be treated like a simple blackbody.
Ron C. replied:
David, thanks a lot for your comment. I take it that your traffic analogy refers to the flow of energy from the surface through the atmosphere to space. And in that case, the sun is like an assembly plant where cars are rolling into our system at a (mostly) constant rate. When the traffic jams, the additional cars continue to fill the road because they are impeded from turning off into space. An interesting point is the role of the oceans as a kind of parking lot with a variable release of cars onto the road, and thus acts as a buffer between the factory and the traffic flow.
I want to think next about the mechanisms at the interface between oceans and air.
On April 24 David A. said:
Thank you Ron. To clarify, The highway is the earth’s system, defined as the “oceans, land, and atmosphere”, the on ramp is Total Solar Insolation, and the off ramp is radiation to space. So in this context albedo radiation is a Lamborghini, and the ocean is gridlock (or parking lot as you said) on the highway. Yes, the ocean is the dog, and the atmosphere is the tail, and a snubbed one at that.
A practical example is seen annually. in the SH summer, the earth receives about 7 percent more insolation, (a massive increase in input, close to 90 watts per sq. meter.) yet the atmosphere cools! Is the earth gaining or losing energy in the SH summer? There is certainly reduced residence time in the NH, due to increased albedo of snow on the land mass heavy N.H, and increased residence time in the SH, due to amplified SW ocean penetration. Both factors however remove energy from the atmosphere; the NH through reflecting energy to space, and the SH via absorbing the energy into the oceans, away from the atmosphere for much longer periods. So, despite a massive increase in insolation, the atmosphere cools, but does the earth gain or lose energy? I am guessing that it gains energy, unless SH cloud cover greatly expands, but I have never seen this quantified.
All non-input change theories on climate are a manifestation of the affect of “residence time.” I have found this useful in talking to “Slayers” I tell them the GHE is based on increasing the residence time of certain WL of LWIR energy via redirecting exiting LWIR energy back into the system, while input remains constant, thus more total energy is within the system. The greater the increase in residence time of the energy, the greater the potential energy accumulation.
In “slayers” defense I will say that some of the energy in the atmosphere is the result of conduction, and if conducted energy manifesting as heat strikes a GHG molecule, and is causative to that GHG molecule sending that energy to space, then said GHG molecule is cooling, as otherwise the conducted energy would have stayed within the atmosphere if it had simply conducted to another non GHG molecule. I have been unsuccessful in getting anyone to quantify how often this happens. In the lower atmosphere collision, or conduction transfers dominate and GHG molecule function pretty much the same as non GHG molecules, transferring energy via collision more rapidly then via radiation.
In this sense I maintain not all watts are equal. In a past WUWT post Willis asserted that the LWIR re-striking the surface, via back radiation, was equal to the SW striking the surface, sans the clouds presence. I maintained that while the watts may be equal, the SW was causative to a much greater overall energy within the “system” due to it longer residence time striking and penetrating the tropical SH ocean, up to 800 feet deep. ( the epipelagic Zone ) and some even deeper to 3000′ (Mesopelagic Zone)
The interchange between the ocean and the atmosphere is a very active place. My understanding is that the oceans are, on average, a bit warmer then the surface atmosphere. (The dog is wagging the tail)
Regarding LWIRs ability to heat the ocean, I am often struck by how black and white the argument usually goes; as in…”LWIR cannot warm the oceans”. The counter argument goes, “can to”. I watched a very long post at WUWT go on and on like that. I tried once or twice to say wait a minute guys, let quantify this, or admit we don’t know. In general I think most of the energy of LWIR goes into evaporation, convection, and energy release through condensing at altitude, and radiation lost to space. However I can see the potential for the surface in some areas to warm, and slow the release of ocean heat. But if the state of our climate science is such that we do not know the answer to this in detail, then this alone, ignoring a dozen other major unknowns, is, IMV, adequate to completely discount the models.
Ron C. responds:
David, I am stimulated by this discussion and am posting it separately for others’ interest.
Your point about SH summer provides observational confirmation of the effects of thermal storage in the oceans.
Previously I have thought about your points in terms of the delay in heat transport from surface to space. Surrounded by the nearly absolute cold of space, our planet’s heat must move in that direction, which involves pushing it through the atmosphere. Of course, you are right that there is an additional delay within the oceans from the overturning required to bring energy to the surface for cooling. I like the image above depicting the water wheel as a massive traffic circle.
The Difference between climate on the Earth and the Moon
The intensity of solar energy is the same for the Earth and Moon, yet the dark side of the earth is much warmer than the dark side of the moon. And the bright side of the earth is much cooler than the bright side of the moon. Why are the two climates so different?
Earth’s oceans and atmosphere make the difference. Incoming sunlight is reduced by gases able to absorb IR and also by reflection from clouds and non-black surfaces. The earth’s surface is heated by sunlight, much of it stored and distributed by the oceans (71% of the planet surface). The atmosphere delays the upward passage of heat, and like a blanket slows the cooling allowing a buildup of temperature at the surface until there is a balance of heat radiating to space from the sky to match the solar energy coming in.
How the Atmosphere Processes Heat
There are 3 ways that heat (Infra-Red or IR radiation) passes from the surface to space.
1) A small amount of the radiation leaves directly, because all gases in our air are transparent to IR of 10-14 microns (sometimes called the “atmospheric window.” This pathway moves at the speed of light, so no delay of cooling occurs.
2) Some radiation is absorbed and re-emitted by IR active gases up to the tropopause. Calculations of the free mean path for CO2 show that energy passes from surface to tropopause in less than 5 milliseconds. This is almost speed of light, so delay is negligible.
3) The bulk gases of the atmosphere, O2 and N2, are warmed by conduction and convection from the surface. They also gain energy by collisions with IR active gases, some of that IR coming from the surface, and some absorbed directly from the sun. Latent heat from water is also added to the bulk gases. O2 and N2 are slow to shed this heat, and indeed must pass it back to IR active gases at the top of the troposphere for radiation into space.
In a parcel of air each molecule of CO2 is surrounded by 2500 other molecules, mostly O2 and N2. In the lower atmosphere, the air is dense and CO2 molecules energized by IR lose it to surrounding gases, slightly warming the entire parcel. Higher in the atmosphere, the air is thinner, and CO2 molecules can emit IR and lose energy relative to surrounding gases, who replace the energy lost.
This third pathway has a significant delay of cooling, and is the reason for our mild surface temperature, averaging about 15C. Yes, earth’s atmosphere produces a buildup of heat at the surface. The bulk gases, O2 and N2, trap heat near the surface, while IR-active gases, mainly H20 and CO2, provide the radiative cooling at the top of the atmosphere.
Science Matters 